Amide diol extended cathodic electrodeposition resins

Abstract

An improved electrodepositable cationic resin is disclosed. Prior art electrodepositable cationic resins are formed from polyepoxides which are chain extended with polyether or polyester polyols to internally flexibilize the resin. Our polyepoxide resin is chain extended with amide diol which gives a resin which is hydrolytically stable and does not tend to absorb moisture.

We claim: 
     
       1. An improved cationic electrodeposition resin to be used in aqueous cathodic electrodeposition baths wherein the resin is made by chain extending a polyepoxide of a polyglycidyl ether of polyhydric alcohol having about two epoxy groups per molecule with an internal plasticizer wherein the improvement comprises said internal plasticizer being an amide diol which is the reaction product of a diacid and an alkanol amine which has primary alcohol and primary amine terminating groups or is the reaction product of a diprimary amine and epsilon-caprolactone. 
     
     
       2. The resin of claim 1 wherein the amide diol is a condensation product of a diacid and an alkanol amine which has primary alcohol and primary amine terminating groups. 
     
     
       3. The resin of claim 1 wherein the amide diol is a reaction product of a di-primary amine and epsilon-caprolactone. 
     
     
       4. A method of coating an electrically conductive article with a cationic electrodeposition resin comprising: (1) mixing the cationic electrodeposition resin of claim 1 with an amine to form a polyepoxy amine adduct;   (2) blending said adduct with an acid, crosslinker, and water to form a principal emulsion;   (3) adding more water and pigment paste to the principal emulsion thereby forming an electrocoat bath;   (4) immersing the article in the electrocoat bath; and   (5) passing a direct current through the article.   
     
     
       5. The resin of claim 2 in which the molar ratio of diacid and alkanol amine is 1.5:1 to 1:1. 
     
     
       6. The resin of claim 3 in which the molar ratio of epilson-caprolactone and diprimary amine is 3:1 to 2:1.